Several experiments show that the biosynthesis of colchicine involves the amino acids phenylalanine and tyrosine as precursors. Indeed, the feeding of C. autumnale with radioactive amino acid, tyrosine-2-C14, caused the latter to partially incorporate in the ring system of colchicine. The induced absorption of radioactive phenylalanine-2-C14 by C. byzantinum , another plant of the Colchicaceae family, resulted in its efficient absorption by colchicine.  However, it was proven that the tropolone ring of colchicine resulted, in essence, from the expansion of the tyrosine ring. Further radioactive feeding experiments of C. autumnale revealed that colchicine can be synthesized biosynthetically from (S) -autumnaline. That biosynthesic pathway occurs primarily through a para-para phenolic coupling reaction involving the intermediate isoandrocymbine. The resulting molecule undergoes O -methylation directed by S-adenosylmethionine. Two oxidation steps followed by the cleavage of the cyclopropane ring leads to the formation of the tropolone ring contained by N -formyldemecolcine. N -formyldemecolcine hydrolyzes then to generate the molecule demecolcine, which also goes through an oxidative demethylation that generates deacetylcolchicine. The molecule of colchicine appears finally after addition of acetyl-coenzyme A to deacetylcolchicine.